This invention relates to a process for recycling packings containing reactive residues, in particular cartridges for producing polyurethane foam. In the process the packing materials are recovered and the residues contained therein converted into reusable products.
Residue-containing packings as occur for example in great quantities in the form of wholly or partly empty cartridges are increasingly becoming a disposal problem. They cannot be dumped on disposal sites for reasons of environmental protection since, the residues contained therein can pass into the atmosphere, the soil or the groundwater and lead to considerable damage there. The same holds for burning, which is frequently incomplete in particular with chemicotechnical products and produces great quantities of pollutants which can be bound only by elaborate measures, if at all. Burning thus leads to a great reduction in the volume of waste but does not necessarily solve the pollution problem.
Special problems arise when the residues contained in the packings are themselves reactive and possible even toxic products, as is the case for example with isocyanate-containing prepolymers for polyurethane foams. The same holds for other reactive plastic products, for example self-curing or hardenable mixtures for coatings, adhesive mixtures, etc. In the following the problem will be discussed in relation to the disposal of prepolymer-containing cartridges for producing polyurethane foams, this case being given only as an example.
Polyurethane foams have become widely used in many fields. They are commonly used particularly in the construction industry for sealing and insulating, as well as in other technical fields. Polyurethane foams are commonly discharged from cartridges containing a polyurethane prepolymer together with required additives. These cartridges cannot be reused. On the other hand, they are problem waste which cannot be disposed of in the normal way.
In accordance with efforts to limit household and industrial waste, measures are being increasingly discussed and implemented to force manufacturers to take back their product packaging after use and ensure its reuse or disposal themselves. Such measures have made it necessary to find ways of treating such waste economically. The treatment of returned cartridges for polyurethane foam production involves a number of problems which complicate economic recycling. For example, some returned cartridges can be under pressure due to the penetration of moisture during improper storage or treatment, which makes both opening and burning a problem. Furthermore the cartridges have different filling conditions, ranging from overaged cartridges virtually full of prepolymer which cannot be discharged due to a blocked valve, to virtually empty cartridges with only a remainder of prepolymer adhering to the edges in an uncrosslinked to crosslinked state.
Up to now a number of processes have become known for recycling packings, including aerosol cans for polyurethane foam production. For example it has been proposed to pass pressure cans via a sluice system into a plant under inert gas and crush them there. Further, processes have become known for passing aerosol cans into a plant, crushing them there and extracting the ingredients with suitable solvents. In these processes both the packing materials and the ingredients (prepolymer, propellant) are recovered.
However these known processes, some of which are quite efficient and in use, are capable of being improved with regard to industrial safety, process control and efficiency. It is problematic to separate the residues contained in the packings in simple fashion and direct them to suitable reuse. Further problems arise from the fact that the packings contain toxicologically unsafe substances as well as combustible solvents which can yield explosive gas mixtures after opening. In particular these processes are designed for recycling propellant-containing aerosol cans, however, which limits their applicability for pressureless cartridges.